bpftool: clean-up usage of libbpf_get_error()

bpftool is now totally compliant with libbpf 1.0 mode and is not
expected to be compiled with pre-1.0, let's clean-up the usage of
libbpf_get_error().

The changes stay aligned with returned errors always negative.

- In tools/bpf/bpftool/btf.c This fixes an uninitialized local
variable `err` in function do_dump() because it may now be returned
without having been set.
- This also removes the checks on NULL pointers before calling
btf__free() because that function already does the check.

Signed-off-by: Sahid Orentino Ferdjaoui <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alexei Starovoitov <[e-mail]>

tools/bpf/bpftool/btf.c

···
 	int err = 0, i;
 
 	d = btf_dump__new(btf, btf_dump_printf, NULL, NULL);
-	err = libbpf_get_error(d);
-	if (err)
-		return err;
+	if (!d)
+		return -errno;
 
 	printf("#ifndef __VMLINUX_H__\n");
 	printf("#define __VMLINUX_H__\n");
···
 	struct btf *base;
 
 	base = btf__parse(sysfs_vmlinux, NULL);
-	if (libbpf_get_error(base)) {
-		p_err("failed to parse vmlinux BTF at '%s': %ld\n",
-		      sysfs_vmlinux, libbpf_get_error(base));
-		base = NULL;
-	}
+	if (!base)
+		p_err("failed to parse vmlinux BTF at '%s': %d\n",
+		      sysfs_vmlinux, -errno);
 
 	return base;
 }
···
 	__u32 btf_id = -1;
 	const char *src;
 	int fd = -1;
-	int err;
+	int err = 0;
 
 	if (!REQ_ARGS(2)) {
 		usage();
···
 			base = get_vmlinux_btf_from_sysfs();
 
 		btf = btf__parse_split(*argv, base ?: base_btf);
-		err = libbpf_get_error(btf);
 		if (!btf) {
+			err = -errno;
 			p_err("failed to load BTF from %s: %s",
 			      *argv, strerror(errno));
 			goto done;
···
 		}
 
 		btf = btf__load_from_kernel_by_id_split(btf_id, base_btf);
-		err = libbpf_get_error(btf);
 		if (!btf) {
+			err = -errno;
 			p_err("get btf by id (%u): %s", btf_id, strerror(errno));
 			goto done;
 		}

tools/bpf/bpftool/btf_dumper.c

···
 		goto print;
 
 	prog_btf = btf__load_from_kernel_by_id(info.btf_id);
-	if (libbpf_get_error(prog_btf))
+	if (!prog_btf)
 		goto print;
 	func_type = btf__type_by_id(prog_btf, finfo.type_id);
 	if (!func_type || !btf_is_func(func_type))

tools/bpf/bpftool/gen.c

···
 	int err = 0;
 
 	d = btf_dump__new(btf, codegen_btf_dump_printf, NULL, NULL);
-	err = libbpf_get_error(d);
-	if (err)
-		return err;
+	if (!d)
+		return -errno;
 
 	bpf_object__for_each_map(map, obj) {
 		/* only generate definitions for memory-mapped internal maps */
···
 		/* log_level1 + log_level2 + stats, but not stable UAPI */
 		opts.kernel_log_level = 1 + 2 + 4;
 	obj = bpf_object__open_mem(obj_data, file_sz, &opts);
-	err = libbpf_get_error(obj);
-	if (err) {
+	if (!obj) {
 		char err_buf[256];
 
+		err = -errno;
 		libbpf_strerror(err, err_buf, sizeof(err_buf));
 		p_err("failed to open BPF object file: %s", err_buf);
-		obj = NULL;
 		goto out;
 	}
 

tools/bpf/bpftool/iter.c

···
 #ifndef _GNU_SOURCE
 #define _GNU_SOURCE
 #endif
+#include <errno.h>
 #include <unistd.h>
 #include <linux/err.h>
 #include <bpf/libbpf.h>
···
 	}
 
 	obj = bpf_object__open(objfile);
-	err = libbpf_get_error(obj);
-	if (err) {
+	if (!obj) {
+		err = -errno;
 		p_err("can't open objfile %s", objfile);
 		goto close_map_fd;
 	}
···
 
 	prog = bpf_object__next_program(obj, NULL);
 	if (!prog) {
+		err = -errno;
 		p_err("can't find bpf program in objfile %s", objfile);
 		goto close_obj;
 	}
 
 	link = bpf_program__attach_iter(prog, &iter_opts);
-	err = libbpf_get_error(link);
-	if (err) {
+	if (!link) {
+		err = -errno;
 		p_err("attach_iter failed for program %s",
 		      bpf_program__name(prog));
 		goto close_obj;

tools/bpf/bpftool/main.c

···
 			break;
 		case 'B':
 			base_btf = btf__parse(optarg, NULL);
-			if (libbpf_get_error(base_btf)) {
-				p_err("failed to parse base BTF at '%s': %ld\n",
-				      optarg, libbpf_get_error(base_btf));
-				base_btf = NULL;
+			if (!base_btf) {
+				p_err("failed to parse base BTF at '%s': %d\n",
+				      optarg, -errno);
 				return -1;
 			}
 			break;

tools/bpf/bpftool/map.c

···
 	if (info->btf_vmlinux_value_type_id) {
 		if (!btf_vmlinux) {
 			btf_vmlinux = libbpf_find_kernel_btf();
-			err = libbpf_get_error(btf_vmlinux);
-			if (err) {
+			if (!btf_vmlinux) {
 				p_err("failed to get kernel btf");
-				return err;
+				return -errno;
 			}
 		}
 		*btf = btf_vmlinux;
 	} else if (info->btf_value_type_id) {
 		*btf = btf__load_from_kernel_by_id(info->btf_id);
-		err = libbpf_get_error(*btf);
-		if (err)
+		if (!*btf) {
+			err = -errno;
 			p_err("failed to get btf");
+		}
 	} else {
 		*btf = NULL;
 	}
···
 
 static void free_map_kv_btf(struct btf *btf)
 {
-	if (!libbpf_get_error(btf) && btf != btf_vmlinux)
+	if (btf != btf_vmlinux)
 		btf__free(btf);
 }
 
 static void free_btf_vmlinux(void)
 {
-	if (!libbpf_get_error(btf_vmlinux))
-		btf__free(btf_vmlinux);
+	btf__free(btf_vmlinux);
 }
 
 static int

tools/bpf/bpftool/prog.c

···
 		return;
 
 	btf = btf__load_from_kernel_by_id(map_info.btf_id);
-	if (libbpf_get_error(btf))
+	if (!btf)
 		goto out_free;
 
 	t_datasec = btf__type_by_id(btf, map_info.btf_value_type_id);
···
 
 	if (info->btf_id) {
 		btf = btf__load_from_kernel_by_id(info->btf_id);
-		if (libbpf_get_error(btf)) {
+		if (!btf) {
 			p_err("failed to get btf");
 			return -1;
 		}
···
 		open_opts.kernel_log_level = 1 + 2 + 4;
 
 	obj = bpf_object__open_file(file, &open_opts);
-	if (libbpf_get_error(obj)) {
+	if (!obj) {
 		p_err("failed to open object file");
 		goto err_free_reuse_maps;
 	}
···
 		open_opts.kernel_log_level = 1 + 2 + 4;
 
 	obj = bpf_object__open_file(file, &open_opts);
-	if (libbpf_get_error(obj)) {
+	if (!obj) {
 		p_err("failed to open object file");
 		goto err_close_obj;
 	}
···
 	}
 
 	btf = btf__load_from_kernel_by_id(info.btf_id);
-	if (libbpf_get_error(btf)) {
+	if (!btf) {
 		p_err("failed to load btf for prog FD %d", tgt_fd);
 		goto out;
 	}

tools/bpf/bpftool/struct_ops.c

···
 		return btf_vmlinux;
 
 	btf_vmlinux = libbpf_find_kernel_btf();
-	if (libbpf_get_error(btf_vmlinux))
+	if (!btf_vmlinux)
 		p_err("struct_ops requires kernel CONFIG_DEBUG_INFO_BTF=y");
 
 	return btf_vmlinux;
···
 	const char *st_ops_name;
 
 	kern_btf = get_btf_vmlinux();
-	if (libbpf_get_error(kern_btf))
+	if (!kern_btf)
 		return "<btf_vmlinux_not_found>";
 
 	t = btf__type_by_id(kern_btf, info->btf_vmlinux_value_type_id);
···
 	}
 
 	kern_btf = get_btf_vmlinux();
-	if (libbpf_get_error(kern_btf))
+	if (!kern_btf)
 		return -1;
 
 	if (!json_output) {
···
 		open_opts.kernel_log_level = 1 + 2 + 4;
 
 	obj = bpf_object__open_file(file, &open_opts);
-	if (libbpf_get_error(obj))
+	if (!obj)
 		return -1;
 
 	set_max_rlimit();
···
 
 	err = cmd_select(cmds, argc, argv, do_help);
 
-	if (!libbpf_get_error(btf_vmlinux))
-		btf__free(btf_vmlinux);
+	btf__free(btf_vmlinux);
 
 	return err;
 }